Chakra control is something not every ninja can just learn, Kakashi even started in part 1 that not even Sasuke nor the other rookies can compete with Sakuras chakra control during the fight between her and Ino.
not with Hinata in the same group as her basic gentle fist requires more chakra control than 20-something Kabuto’s medic scalpel.
which is something Tsunade said surpassed her.
And a seal is not something just anyone can learn either, if it were, the Uzumaki wouldn’t have been as feared but they were.
You can’t just downplay the Uzumaki’s abilities to make Sakura look good. You can’t erase the fact that most of Tsunade’s abilities and ideas came from the very clan Karin was born into
and that she is said to have extensive knowledge already.
Cheloneuniverse 